Efficient Use of Nutrient Applied as Starter Fertilizer
Progress Report December 31, 2010
Daniel Kaiser and Bruce Potter
University of Minnesota
Introduction
Nutrients contained in liquid fertilizers typically cost more per pound then equivalent
nutrients from dry fertilizer sources. Liquid fertilizers are typically used as starter
fertilizers applied with the planter on the corn seed. Thus, efficient use of the right
nutrients in the right amounts in critical in assuring the economical use of nutrients in
corn production. Starter fertilizer is typically used as a supplement to broadcast fertilizer
application in order to speed up growth when conditions are not favorable in the spring.
Past research has found that typically phosphorus or nitrogen is responsible for increases
in early plant growth. However, early plant growth is not always translated into higher
crop yields. In addition, many starter mixes also contain potassium and previous research
has shown positive yield benefits under high K soil test levels from banded applications,
particularly deep banded K, on corn yield. Since N and P can influence early plant
growth does this benefit the uptake of all nutrients, particularly K when it is or is not
applied.
Study Objectives
1) Determine the effect of N, P, and K applied alone and in combination of corn
yield and growth.
2) Study the effect of starter fertilizer combinations on stalk damage at the end of the
growing season.
This report outlines the design and summary of trial locations for 2010. Five new
locations were initiated across Minnesota for the final year of this study. Locations of
field trials and soil test averages are listed in Table 1. Identical corn near isolines of
Dekalb 52-59VT3/52-63RRYGCB and 38-89VT3/38-92RR were used. The 52-59/52-63
hybrid set was used in 2010 replacing 50-44/50-48 which was not available for 2010 for
southern locations. Starter was applied at rates of 10 lbs of N, 20 lbs of P2O5, and 20 lbs
of K2O applied in combinations of N only, N+P, K only, N+K, and N+P+K and were
compared to a non-starter control (CHK). Starter was applied with the planter in a band
two inches beside and below the seed furrow. Within each starter treatment two hybrids
were planted side by side in eight row strips 60 feet long. Corn was planted at 35,000
seeds per acre at all locations.
Preliminary Results – 2010 Early Plant Growth and Nutrient uptake, biomass at
maturity, and stalk damage
Early plant growth data, nitrogen, phosphorus, and potassium uptake are given in tables
2, 3, 4, and 5, respectively. Early growth and nutrient uptake were seldom affected by
starter fertilizer application and did not differ between hybrids at any locations. The only
exceptions were increased P uptake at the Redwood location and K uptake at the Olmsted
location. At the Redwood location P uptake was increased when starter P was applied.
Uptake was increased by 20% when N was applied with P with or without K. At the
Olmsted location there was a slightly higher trend for increased P uptake that was close
to the accepted significance but failed to reach the 0.10 accepted level. However, the
same treatments increased K uptake at this location. This effect was seen for both when
K was or was not applied with P. The increased uptake of K was likely due to increased
early growth which followed a clear trend but was not significant. The lack of significant
differences between hybrids indicates that neither hybrid differed in the uptake of
nutrients early in the season. This result was not unexpected and followed past results.
All trials were planted in mid April in 2010. A small growth increase would be expected
due to the early planting date, but the warm early season conditions may have limited
potential for a response to starter N, P, or K.
Plant biomass was measured at the end of the growing season by sampling 6 plants from
each plot at every location. Average plant mass was the greatest at the Clay Co. location
and lowest at Redwood Co and similar at the other three sites (Table 6). At the Olmsted
and Sibley Co. locations plant mass was greater with the double stack hybrid. Starter
fertilizer treatment did not increase or decrease plant mass at the end of the growing
season at any location which is similar to no effect on early plant growth. The increased
plant mass at the Olmsted site was surprising since there was significant rootworm
pressure causing lodging in the double stack hybrid. Total stalk damage, which includes
lodging and stalk rot, is given in Table 7. The amount of stalk damage ranged from 4 to
50% of plants at all locations and was greatest at the Olmsted location and smallest at the
Clay Co. site. The double stack hybrid exhibited less total damage at all locations except
for at Olmsted Co. in which they did not differ. However, stalk lodging from rootworm
injury constituted a majority of the total damage for the double stack hybrid at this site.
At the other locations the difference in damage was not fully related to rootworm
pressure in which the highest pressures were seen at the Olmsted and Redwood Co.
locations. Starter fertilizer affected damage ratings at the Clay and Sibley Co. locations.
Damage was slightly higher at Clay Co. and lower at Sibley Co. when starter was applied
and there was no clear effect of specific nutrients. Potassium has been noted to help with
the plants ability to lessen the effects of disease and potentially insect pressures. From
our data there does not seem to be any clear effect on damage from K application. Since
this report only is a preliminary summary a further summary of the multi-year data will
be conducted.
Corn Grain Yield and Moisture
Corn grain yield was not affected by starter fertilizer use at any location (Table 8). The
only significant yield differences were seen between hybrids at all locations except for
Renville Co. At Redwood, Clay, and Olmsted Co. sites the triple stack hybrid produced
greater yields than the double stacks. At the Redwood and Olmsted sites this was likely
due to rootworm injury early in the season. At Clay Co. there was no rootworm pressure
and not clear differences in hybrids except for some potential differences in damage.
Parts of this location were flooded early in the growing season which affected yields on
one-third of the trial area, but there was no trend in this damage affecting one hybrid
more than another. The yield difference between the triple and double stack was the
greatest at the Olmsted location where rootworm injury was the greatest (not shown). At
the Sibley Co. location the triple stack variety yielded slightly less than the double. This
effect was seen in the same field in 2008 as well as other fields with high yield potentials
and little to no rootworm pressure early.
It appears that in the presence of corn rootworm there is a significant yield and economic
benefit to using a resistant hybrid but at times there is a small yield advantage to the
double stack in the absence of rootworm pressure. The potential advantage in that
particular situation is far less than the difference between a triple and double stack
hybrid. Therefore, the triple stack seems to be a better choice for risk management unless
the potential for rootworm injury can be assessed early in the growing season. Data from
the previous two years of the study agrees with this assessment, but differs in the fact that
starter K appeared to increase yields slightly by an average of 4 bu/acre in 2008 and
2009. All locations studied over the three years of this project have had similar high
testing K soils. Those results indicated a potential benefit to starter K, but no impact on
N or P applied with K on yield. Whether this increase would be economical would
depend on the price of the fertilizer and value of the corn. The 2010 data, analyzed
across locations, did not indicate a similar response to starter K. This may be a reflection
of the early planting dates or the conditions during the growing season. At this time we
cannot determine why there was a difference between responses for the years, but there
likely is some impact due to differences in trial locations. Grain moisture is also studied
in addition to yield due to potential for dryer grain following starter application, but there
was no difference in grain moisture at harvest due to starter fertilizer application at any
location (Table 9).
Project Work for 2011
The final year of this trial was the 2010 growing season. At this time we are in the
process of final data summary for a final report. The remaining work includes:

Analysis of R6 plant and grain data from the 2010 trials

Summary of root injury ratings and plant damage ratings from 2008-2010

Final data summary for final project report
Currently, the final report is planned to be finished before Summer of 2011.
Table 1. Summary of soil test data from 2010 starter locations.
Table 2. Early corn growth (V4-V6) summarized by starter fertilizer treatment and hybrid
averages. Statistics are given for ANOVA conducted for main treatment effects and their
interaction. Treatments are considered significant at P<0.10.
Table 3. Early corn N uptake (V4-V6) summarized by starter fertilizer treatment and
hybrid averages. Statistics are given for ANOVA conducted for main treatment effects
and their interaction. Treatments are considered significant at P<0.10.
Table 4. Early corn P uptake (V4-V6) summarized by starter fertilizer treatment and
hybrid averages. Statistics are given for ANOVA conducted for main treatment effects
and their interaction. Treatments are considered significant at P<0.10.
Table 5. Early corn K uptake (V4-V6) summarized by starter fertilizer treatment and
hybrid averages. Statistics are given for ANOVA conducted for main treatment effects
and their interaction. Treatments are considered significant at P<0.10.
Table 6. Plant dry matter at R6 (maturity) summarized by starter fertilizer treatment and
hybrid averages. Statistics are given for ANOVA conducted for main treatment effects
and their interaction. Treatments are considered significant at P<0.10.
Table 7. Total stalk damage (lodging and stalk rot ratings) summarized by starter
fertilizer treatment and hybrid averages. Statistics are given for ANOVA conducted for
main treatment effects and their interaction. Treatments are considered significant at
P<0.10.
Table 8. Corn grain yield (reported at 15.5% moisture) summarized by starter fertilizer
treatment and hybrid averages. Statistics are given for ANOVA conducted for main
treatment effects and their interaction. Treatments are considered significant at P<0.10.
Table 9. Corn grain moisture at harvest summarized by starter fertilizer treatment and
hybrid averages. Statistics are given for ANOVA conducted for main treatment effects
and their interaction. Treatments are considered significant at P<0.10.